Industry increasingly depends upon highly automated data acquisition and control systems to ensure that industrial processes are run efficiently, safely and reliably while lowering their overall production costs. Data acquisition begins when a number of sensors measure aspects of an industrial process and periodically report their measurements back to data collection and/or control systems. Such measurements come in a wide variety of forms and are used by industrial process control systems to regulate a variety of operations, both with respect to continuous and discrete manufacturing processes. By way of example the measurements produced by a sensor/recorder include: a temperature, a pressure, a pH, a mass/volume flow of material, a quantity of bottles filled per hour, a tallied inventory of packages waiting in a shipping line, or a photograph of a room in a factory. Often sophisticated process management and control software examines the incoming data, produces status reports, and, in many cases, responds by sending commands to actuators/controllers that adjust the operation of at least a portion of the industrial process. The data produced by the sensors also allow an operator to perform a number of supervisory tasks including: tailor the process (e.g., specify new set points) in response to varying external conditions (including costs of raw materials), detect an inefficient/non-optimal operating condition and/or impending equipment failure, and take remedial actions such as adjust a valve position, or even move equipment into and out of service as required.
Typical industrial processes today are extremely complex and comprise many intelligent devices such as transmitters, positioners, motor drives, limit switches and other communication enabled devices. By way of example, it is not unheard of to have thousands of sensors and control elements (e.g., valve actuators) monitoring/controlling aspects of a multi-stage process within an industrial plant. As field devices have become more advanced over time, the process of setting up field devices for use in particular installations has also increased in complexity.
In previous generations of industrial process control equipment, and more particularly field devices, transmitters and positioners were comparatively simple components. Before the introduction of digital (intelligent) transmitters, setup activities associated with a field device were relatively simple. Industry standards like 3-15 psi for pneumatic instruments or 4-20 ma for electronic instruments allowed a degree of interoperability that minimized setup and configuration of analog transmitters.
More contemporary field devices include digital data transmitting capabilities and on-device digital processors, referred to generally as “intelligent” field devices. Such devices generally support an extensive set of parameters for providing a variety of status and process variable values.
One particular class of intelligent field device incorporates the Profibus protocol/architecture. In process control systems that embody the Profibus protocol, an example of a Profibus device hardware configuration includes a device I/O module and a set of field I/O cards that connect the Profibus device I/O module to a set of field devices. The device I/O module receives data from the set of field I/O cards and merges the received data into a single message string. The single message string is transmitted by the device I/O module of the Profibus device to an I/O module assembly (e.g., an Invensys FBM222).
In the known Profibus systems, the I/O module assembly receives messages from Profibus devices wherein each received message contains the combined data for all signals provided by the field I/O cards installed on a corresponding Profibus device rack. Known I/O module assemblies are programmed to provide the received messages in their unprocessed form to requesting entities such as control processors and system management applications/interfaces. In the known systems, a control processor, configured to execute a set of distributed control interface (DCI) blocks, submits requests for particular individual pieces of information in association with the execution of the DCI blocks. The requests from the control processors pertain to individual pieces of information contained within Profibus messages rather than groups of information provided within Profibus messages. Therefore, a separate request is submitted by a control processor to an I/O module assembly for each piece of information that is read or written.
Profibus device messages potentially carry a variety of information. In addition to providing process variable measurement values, the message data potentially includes a variety of status information provided in the form of status bits. In some instances each status bit is pre-configured to have a particular meaning. Known I/O module assemblies are capable of extracting and forwarding the contents of the received messages, including the status bits, to control processors (in response to the aforementioned DCI block-initiated requests). In some known systems, each status bit is associated with an LED on a Profibus device LED panel, the meaning of which is determined by consulting a user guide associated with the LED panel of the customized Profibus device.